When I am invoicing it would be so nice to be able to select/check multiple time entries and have the total appear for the checked items. Then when I'm invoicing I could easily add up the time for a specific task or tasks instead of exporting the time entries as a .csv and using excel to do the math or adding the time/totals myself.

be able to set workdays, even work hours.

I would need tasks assigned to tasks, if you had this I would buy.

Tasks can have a priority (which is fairly limited) but projects cannot. It would be great if projects could be assigned a priority and even better if the priorities were customizable.

the ability for project owner to reset password or to send email to contact to retrieve password.

In a calendar view see who are connected to a task or an event

Further customization beyond the two choices for page theme and 7 choices for color theme. If your brand does not match those colors that you will not be able to "seamlessly" integrate the system with your site. The is really a key feature in my opinion. Perhaps it would be simple enough to put a color picker in there for each of those two elements if you are not up for a full blown brand integration feature.

Often you have a multitude of subtasks that you don't want to see on your Calendar. Sometimes you might want to see all subtasks.

Why not have a filter for both of these views on Calendar?

Tasks should sync with task list in Outlook.

Syncing tasks with mail would be a huge benefit. Being able check off completed tasks in mail would be great.

Evernote is a very popular tool for taking notes, etc. Recently, the API was made available, making it possible to integrate (see eg. pelotronics). For companies already using evernote, or for companies that have requirements for offline notes (evernote has client apps for mac, windows, iphone, android, etc.) such integration might be very valuable.

In the task view, it would be extremely helpful to see the total number of hours already logged for each task (I.e. as a separate column). While this info is available it's another click away and then you can only see the total one task at a time. Having this info visible in the list view would allow you to get a quick picture of where you are from a budget/hourly standpoint and see which tasks are at risk.

Sometimes you don`t want the user to know how much you are charging for his work. So when entering the timecard the fee should be hidden.

It should be possible to make changes to a conversation. Eg: I’ve just made a conversation and saved it, but now I see a typo…This means I have to delete the conversation and start over.